Script execution in response to activation of the ControlShell.

efore the PFE add-in attempts to pop up the ControlShell window it executes
the script pfeAddin_OnPopUp.py on Excel's main thread. If nothing goes wrong
then the ControlShell pops up. The ControlShell is an out-of-process
application. When the user closes it the ControlShell's process does not die.
It remains in memory awaiting next activation. The ControlShell executes the
script pfeControlShell_init.py in its own process the first time it pops up.
It also executes the script pfeControlShell_Activate.py every time it pops up.

The scripts pfeAddin_OnPopUp.py, pfeControlShell_init.py,
pfeControlShell_Activate.py are all located in the directory "c:\Program
Files\PythonForExcel".